Pulse modulation systems



April 28, 1964 J. P- MAGNIN ETAL PULSE MODULATION SYSTEMS Filed Dec. 20, 1960 dean P. May/7x0 Jfierw/o A. Few/79' ATTOIFIVEV United States Patent 3,131,364 PULSE MODULATIGN SYSTEMS Jean P. Magnin and Sherwin K. Feingold, Sarasota, Fla,

assignors to Electro-Mechanical Research, Inc, Sarasota, Fla, a corporation of Connecticut Filed Dec. 20, 1960, Ser. No. 77,075 7 Claims. (Cl. 332-12) This invention relates to pulse modulation systems including magnetic switching elements and more specifically to such pulse modulation systems having magnetic cores and feedback circuits for controlling the instantaneous flux level therein in response to low level intelligence voltage signals derived from relatively low impedance signal sources.

in modulation systems, use can be made of small high permeability magnetic cores of substantially rectangular B-H hysteresis loops. To that end, an alternating current is applied to a sweep winding on the core. Since a high permeability core requires a very small current to switch from one stable saturated state to the other, output pulses can be derived, either from the sweep winding itself or from an output Winding on the core, which are indicative of the near zero crossings of the sweeping alternating current. When this current is a pure sine wave, for example, the interpulse period of the output pulses is constant. {This interpulse period can be varied or modulated as a function of the intensity and polarity of an intelligence current signal applied to a modulation winding on the core.

In telemetering systems, the intelligence signals are usually derived from low impedance transducers respons-ive to changes in monitored physical quantities such as temperature, pressure, vibration, radiation, etc. Were such a transducer connected directly to the modulation winding, the transducer low impedance would appear substantially as 'a short-circuit across all the other core windings thereby causing the output time modulated pulses to become greatly attenuated or to vanish.

One possible method for overcoming this undesired attenuation is to insert a relatively high resistor in series with the transducer. Such a resistor, however, would consume substantially all of the intelligence signal power.

Another possible method is to insert an inductor instead of a resistor in series with the transducer to avoid the high power consumption. However, the dependence of the inductive impedance on frequency introduces distortions in the frequency and phase of the output time modulated pulses.

Accordingly, it is an object of our invention to provide magnetic switching circuits wherein the deleterious effects caused by the coupling of a relatively low impedance energiziing source to a magnetic core are automatically and substantially eliminated.

Briefly, this is accomplished in accordance with this invention by establishing a fully degenerative feedback loop network between the output winding and the modulation winding on such a core to automatically control the consumption, by the low impedance intelligence source, of electric energy released during the switching of the core from one saturated state to the other.

The novel features of this invention that are considered characteristic are set forth with particularity in the appended claims. The invention itself both as to its organization and method of operation, as well as additional objects and advantages thereof, will be best under stood from the following description when read in connection with the drawing in which the sole figure represents a schematic diagram of a magnetic regulating system in accordance with a preferred embodiment of our invention.

Referring to the drawing, a high pemeability core 1,

3,131,364 Patented Apr. 28, 1964 preferably characterized by a rectangular B-H hysteresis loop, is switched or swept from one stable state to the other in response to signals generated by a relatively high frequency, high impedance voltage source 2 connected to sweep winding 3.

The switching time of core 1 is controlled or modulated by an intelligence voltage signal derived from a relativel low impedance, low frequency modulating source 4 connected in series circuit relation with modulation winding 5 and feedback winding 6.

To prevent the loading-down of core 1 by the low impedance source 4 and the resulting deterioration of the output modulated pulses, a feedback loop is provided comprising output winding 7, input winding 8, amplifier 9 and control winding 10 all connected in series circuit relation as shown. Windings 6, 8 and 1d are Wound on core 11 of transformer 12. Their respective polarities are indicated by [the conventional dots.

In operation, when core 1 is switched from one remanent saturated state to the other in response to an alternating sweep current i a portion of the magnetic energy stored in the core is converted, during the relatively short switching interval, into electrical energy which induces pulses in each of the core windings. In an ideal core Without losses, the electric energy is equal to the dissipated magnetic energy. The distribution of this electric energy among the windings is dependent upon their respective loads.

Thus during the switching time of the core, induced pulse currents i and i are respectively generated in windings 7 and 5. Current i is amplified by amplifier 9 into i., which is transformed into i in winding 8. The turns ratio and the polarity of windings 8 and 10 are such that i differs in magnitude from i by a very small amount 6 and is out of phase therewith. The respective current polarities are represented by arrows. This small difference current e is again amplified into i, which is transformed into i in winding 6. I'he turns ratio and the polarity of windings 6 and 10 are such that i is substantially equal in magnitude to i;, and is 180 out of phase therewith. All the above detailed steps are carried out substantially instantaneously with the result that the flux changes in the core produce no appreciable flow of net pulse current in the modulation winding.

Therefore, since the current i induced in winding 5 by the changes in the magnetic flux in core 1, is at all times opposed by an equal injected feedback current i the low impedance modulation source 4 is prevented from consuming any pulse power and, hence, from greatly attenuating the output modulated pulse wave. This time modulated pulse wave is applied to a utilization dew/ice 13 such as a transmitter, for example, which may be connected to the output of amplifier 9 or to any winding of the system.

Obviously, many other modifications and variations of our invention are possible in the light of the above detailed teachings. It should therefore be clear that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A voltage controlled pulse generator comprising in combination: a first magnetic core, a variable low impedance intelligence signal source, a first winding magnetically coupled to said first core to reciprocally convert electromagnetic energy, a second winding magnetically coupled to said first core to convert changing magnetic flux in the core into electric pulses, a third winding, means connecting said intelligence source, said first winding and said third winding in electric series circuit relaton to time modulate said pulses; a fourth winding, an amplifier, a fifth winding, a second magnetic core, means connecting said second and said fourth windings to the 3 input circuit of said amplifier, means connecting said fifth Winding to the output circuit of said amplifier, said third, said fourth and said fifth windings being magnetically coupled to said second core, and a utilization device coupled to the output of said amplifier to receive the modulated pulses.

2. The combination in claim 1 and further including: a sixth winding magnetically coupled to said first core, a frequency sweep signal source, and means connecting said sweep signal source to said sixth Winding.

3. A pulse modulation system for varying the interp ulse period of a pulse Wave in response to an intelligence signal comprising in combination: a first magnetic core and a second magnetic core; a first, second, third, fourth, fifth, and sixthw indings; said first, second and third windings being coupled with said first magnetic core and forming a first magnetic circuit, said fourth, fifth and sixth windings being coupled with said second magnetic core and forming a second magnetic circuit, a relatively high frequency signal source coupled to said first Winding, a relatively low frequency intelligence signal source, means connecting said intelligence signal source, said third and said sixth windings in series circuit relation, an amplifier having an input and output circuit, means coupling said second and said fourth windings to said input circuit, means connecting said fifth winding to said output circuit of said amplifier, and a utilization device coupled to said output circuit for receiving the modulated pulses.

4. In combination means establishing a magnetic circuit, means inducing variations of flux in said circuit, a first Winding linking With said flux for providing an output signal corresponding to said variations, a high input impedance feedback system coupled to said first Winding for transforming said output signal into a corresponding feedback signal, a second winding linking with said fiux, said second winding having a terminal for receiving an energizing signal from a low impedance signal source, said second winding having an induced signal therein corresponding to said variations, and means coupling said feedback system to said second winding for combining said feedback signal in subtractive relation with said induced signal.

5. In combination, means establishing a magnetic circuit, a first winding, a relatively high frequency signal source coupled to said first winding for causing variations of flux in said circuit, a second winding linking with said flux for providing an output signal in correspondence with said variations, a high input impedance feedback system for transforming said output signal into a corresponding feedback signal, a third winding linking with said flux; a relatively low frequency, low impedance signal source coupled to said third winding for controlling said flux,

said third winding having an induced signal therein in correspondence with said variations, and means connecting said feedback system to said third Winding for algebraically adding said feedback signal to said induced signal thereby substatially increasing the apparent impedance of said low frequency source.

6. In combination, a first magnetic core, a low impedance intelligence signal source, a first winding mounted on said core, a second winding mounted on said core, a third winding, means connecting said intelligence source, said first Winding and said third winding in electric series circuit relation, a fourth Winding, an amplifier, a fifth winding, a second magnetic core, means connecting said second and said fourth windings to the input circuit of said amplifier, means connecting said fifth winding to the output circuit of said amplifier, said third, said fourth and said fifth windings being magnetically coupled to said second core, and a sixth winding mounted on said first core and having a terminal for receiving a high frequency signal.

7. A magnetic modulation system comprising in corn bination:

a first magnetic core capable of assuming two stable saturated states,

first means including a first winding magnetically coupled to said first magnetic core for alternately switching the magnetic flux therein from one of said states to the other,

second means including a second winding magnetically coupled to said core to control the time of occurrence of said switching,

and a feedback circuit including a second core coupled to said first core,

said feedback circuit. including a third winding connected to said second winding, said third winding having a voltage induced therein having a magnitude and direction to render the input impedance of said feedback circuit very high thereby reducing the interchange of energy between said first magnetic core and said second means.

References Cited in the file of this patent UNITED STATES PATENTS 2,070,666 Llewellyn Feb. 16, 1937 2,700,130 Ge-yger Ian. 18, 1955 2,901,555 Klinkhamer et al. Aug. 25, 1959 2,905,906 Kittl Sept. 22, 1959 2,926,311 Gab'or Feb. 23, 1960 2,970,224 Lipkin et al. Ian. 31, 1961 2,997,664 Jensen Aug. 22, 1961 3,046,532 Broadbent July 24, 1962 

4. IN COMBINATION MEANS ESTABLISHING A MAGNETIC CIRCUIT, MEANS INDUCING VARIATIONS OF FLUX IN SAID CIRCUIT, A FIRST WINDING LINKING WITH SAID FLUX FOR PROVIDING AN OUTPUT SIGNAL CORRESPONDING TO SAID VARIATIONS, A HIGH INPUT IMPEDANCE FEEDBACK SYSTEM COUPLED TO SAID FIRST WINDING FOR TRANSFORMING SAID OUTPUT SIGNAL INTO A CORRESPONDING FEEDBACK SIGNAL, A SECOND WINDING LINKING WITH SAID FLUX, SAID SECOND WINDING HAVING A TERMINAL FOR RECEIVING AN ENERGIZING SIGNAL FROM A LOW IMPEDANCE SIGNAL SOURCE, SAID SECOND WINDING HAVING AN INDUCED SIGNAL THEREIN CORRESPONDING TO SAID VARIATIONS, AND MEANS COUPLING SAID FEEDBACK SYSTEM TO SAID SECOND WINDING FOR COMBINING SAID FEEDBACK SIGNAL IN SUBTRACTIVE RELATION WITH SAID INDUCED SIGNAL. 